Routing tool



United States Patent 3,381,728 ROUTING TOOL Milton Goldstein, Long Beach, N.Y., assignor to John Barsha and A. Abba Orlinger, both of New York, N.Y., and said Milton Goldstein, as trustees for the benefit of themselves and others, with respective alternate trustees Filed Mar. 7, 1966, Ser. No. 532,387 3 Claims. (Cl. 144219) This application is a continuation-in-part of my copending application Ser. No. 282,044 filed May 21, 1963 now Pat. No. 3,238,980, which in turn was a continuation-in-part of my then co-pending application Ser. No. 765,572 filed Oct. 6, 1958 and now abandoned.

This invention is that of a new router bit which provides a very effective advantage, for example, in routing operations on various wood products such as door and their frame jambs, for example, by enabling routing directly significantly larger recesses than heretofore possible by simpler operation. This router bit can cut out in a single position in such wooden objects recesses up to two inches in diameter, and even much greater, without any side to side motion. It thereby enables, for example, preparing with the barest minimum of motions a pair of opposed semi circular hinge recesses in adjacently positioned door and jamb.

This new router bit accomplishes such improved result by having on its recess-cutting face a plurality of pairs of two differently shaped and differently positioned cutting teeth; which pair are located symmetrically about the axis of rotation of the cutting face to provide smooth balance during rotation.

A feature of the invention is that the respectively differently shaped two teeth in each pair have their cutting edges so differently located across the cutting face of the router bit that together they enable during a single rotation of the bit to cut material away from an area equal to that of a circule having the longthe diameter of the cutting tool face, and without side to side motion of the tool.

Another feature of the router bit of the invention is that it readily is applicable to, and provides an advantage in operation and cost in, cutting hinge recesses in a door and a frame jamb, for example, when held adjacently positioned for substantially simultaneously continuous operation on both of them, as in the door and frame holding apparatus of my co-pending application Ser. No. 282,044, now Patent No. 2,238,980.

Further features and advantages of the router bit of the invention are seen from the detailed description below of an illustrative, but not to be restrictive, embodiment of it shown in the accompanying drawings wherein:

FIG. 1 is a perspective view of the router bit;

FIG. 2 is an elevational view of FIG. 1 with its cutting teeth depending;

FIG. 3 is a bottom plan view of FIG. 2;

FIG. 4 is a fragmentary partially sectional view through a hinge recesses-cutting assembly (e.g., 118 of FIG. 2 of my application Ser. No. 282,044 and paralleling its plane thereof) with the router bit carried by an operating motor for it and in operating position within corresponding recesses routed by it in the door and adjacent part of the hinge-carrying jamb;

FIG. 5 is a fragmentary elevational view of part of the door and jamb, with a hinge whose butt plates are semicircular in their outer boundary, inserted and fastened in corresponding hinge recesses semi-circularly shaped and;

FIG. 6 is a vertical sectional view of the line 66 of FIG. 5 in the direction of the arrows.

The router bit of the invention includes primarily (i) a short, stubby cylindrical, rather disc-like cutter head body 191 (taken as a whole) from which two diametrically opposed segments are cut away, one along each of two parallel chords (each being spaced advantageously somewhat more than half a radius from the' body axis), whereby the peripheral cylindrical surface of the cutter head body consists of the two opposed sub-. stantially flat surfaces 192 and 193, each end of each of which respectively joints an adjacent end of each of, so as to be continuous with, the two diametrically opposed substantially circular peripheral portions 194 and 196 of the cutter head body 191;

(ii) mounting means for enabling connecting the router bit with means to rotate it, such as motor "112, which mounting means may be integral with the body 191, but advantageously, as in this embodiment, is an internally threaded central bore 197, into which can be securely tightly threaded the threaded shorter diametered portion of a stud 198 with its shoulder abutting against the under surface 199 of body 191; and

(iii) on the outer or cutting face of the router, cutting teeth including opposed outer annular ring (advantageously identical) teeth 201 and 202 (conveniently called circular-edge teeth because each of them has a circular edge) and opopsed inner annular ring (advantageously identical) teeth 20-3 and 204 (briefly called inner or triangular teeth).

FIGS. 1 through 4 show that to rout with this router bit of this illustrative embodiment, it must be rotated counter clockwise as one looks at the outermost surfaces of the teeth and directly at the axis of the tool ('FIG. 4). Thus, the leading or first cutting corner of each tooth must be the first point or corner of a tooth that is to touch the plane surface of the door D or jamb J to be routed (FIG. 4). That will be the respective corner a of each of the two circular teeth, i.e. which corners are at the outer ends of the diameter a-a (FIGS. 1 and 3) of the largest circle which can be traced by any two diametrically opposed points of any of the teeth.

So also, the leading or first cutting corner of the triangular teeth is the respective corner a of each of them, i.e., at the outer ends of the diameter a'--a (FIG. 3) of the largest circle which can be traced by any point of any inner tooth.

Thus, the leading planar surface area, or fiat, cutting edge of the circular teeth must be the cutting edge along the line ab of each of them, and of the inner teeth is the line a'-b' of each triangular tooth. All of the flat cutting edges of both sets of teeth fall in the same fiat plane.

To provide an adequate clearance, from beyond the leading planar cutting edge a-b of each circular tooth, each point along the edge arced line a-c as well as along the straight line b-c is progressively lower and lowest at the point c (i.e., in the direction toward the rear or undersurface of the router body). Thereby the plane abc slopes thus downwardly (as in FIG. 1) from the line a-b to the point c, or upwardly (as in FIG. 2) from the point a to the corner at the right hand end, whereby that latter line inclines upwardly at an angle, say 8 degrees from the horizontal (FIG. 2).

Similarly, each of the points from the line a'b' along the line a'c and also along the line b-c' of the triangular teeth is progressively lower and lowest at the point 0', as viewed in FIG. 1, so that the plane a'b'c' inclines downwardly from line a'b to point c an adequate amount to provide a sutficient clearance.

The leading or first depth cutting edge (i.e., parallel to the axis of the router bit) of each circular tooth is its vertical edge line a-d; and so also for each triangular tooth is the vertical edge line a'd of each of them.

The angle between each flat cutting edge a-b and the diameter drawn through the axis, of the router and the two leading points a must be adequate to provide a sulficient angle of rake with respect to those cutting edges, and the species of wood to be cut, i.e., whether hard or soft as to its cutting properties. Obviously, the angle of rake as to a circular-edge tooth is changed by varying the length of the dragging edge b-c, as by shortening it starting at the point b, which likewise is done as to a triangular tooth by shortening its dragging edge bc.

The circle drawn through the points a of the inner teeth at least should touch, but preferably merely sufficiently should overlap, the circle drawn through the points b of the outer or circular teeth to assure giving the recess to be cut a clean planar surface. The spacing between the closest two vertical faces of any two of the adjacent teeth should be adequate at least to provide sufiicient egress of shavings resulting from the routing.

Also, each element along the outer cylindrical surface of each cylindrical tooth from its vertical edge a-d to the element drawn through the point is prorgessively further radially inwardly removed (i.e., from a regular circular cylinder drawn through the diametricallyopposed elements a-d) to provide sufiicient relief against cutting friction as the bit rotates. The angle abc of each circular tooth need not be obtuse (as seen in FIGS. 1 and 3). It may be right or even acute, so long as each of these teeth has sufficient material to have adequate strength under its continuing work load, and so long as there is suflicient area of egress for the shavings produced by the routing.

Likewise, it does not matter what is the specific shape of line b-c, or a'c or b-c' of the inner teeth.

Each of the lines ab' does not lie on a diameter of the bit. Instead in going from the point a to its end b, such line a'b' is offset in a direction away from a diameter drawn through the line a'a' (i.e., toward the point c) and to an adequate amount to provide a suificient angle of rake for such inner tooth. In this embodiment, the teeth of each set best are laid out diametrically opposite the respectively corresponding tooth of the other set.

The router bit need not be restricted to having merely two opposed sets of these different types of teeth, for more sets can be used. Thus, for example, with three sets of the two types of teeth each tooth in each set advantageously can be located at a site 120 circular-wise away from the corresponding tooth of each of the other two sets. In that way, as is advantageous in all cases, the respective teeth of each set should be so spaced from the corresponding teeth of the next adjacent set to provide substantial balance during rotation. That thereby avoids during the routing operation any unnecessary vibration or strain on the router bit in its continuous rotation over long periods of service.

The router bit of the invention can be used for any suitable routing operation, particularly for routing recesses and holes whose diameter or shorter dimension extends to about 2 inches and even up to 2.5 inches and greater. It is advantageously effective in routing hinge recesses in doors and their corresponding frame jambs. For such use, the diameter taking in the opposed points aa of the router bit can be equal to twice the difference between (i) the thickness of the door D and (ii) the practical thickness (i.e., reliability to resist easy breakage in handling) of the flange between the outer edge of long side of the door and the nearest tangent to the semi-circular shape of the recess produced by the router bit and parallel to thatedge of the door.

Such flange thickness can be from one-eighth to about a quarter of an inch. Hence, for a door of one and threeeighths inches thickness, the greatest diameter across this router bit can be from about two and one-quarter inches and the other in the correspondingly adjacent position in the jamb) of a joint overall length of from about two and one-quarter inches to perhaps at most two and onehalf inches along the length of the door.

In routing such a pair of complementary recesses, the special router need only be moved repeatedly in a single direction (i.e., from and to a door D and jamb I and back) and advanced into them only far enough to provide the required recess depth. In other words, no motion in either direction along the length of the door or jamb is needed with this special router. Thereby it provides semicircularly shaped recesses to accommodate butt hinges with each leaf having a semi-circular outer periphery.

It readily is seen from the foregoing description of the invention in this router bit and FIGS. 46 how the router bit is used, for example, to prepare such a pair of complementary hinge recesses. Thus, stud 198 of router bit 191 is engaged rigidly by a chuck or collet (not shown) at the outer end of the shaft of motor 112 firmly held in motor support block 110 engaged to horizontal guide track 108 slidably (from right to left in FIG. 4) suspended from plate 84 by opposed slide blocks 100.

With door D and jamb I fixedly supported relative to one another as in FIG. 4, and slide blocks at a starting position further removed to the right, and motor 112 running, motor support block is moved toward depending tongue 104 to advance router 191 between vertical standards 44 to contact the work with the upper surface of guide 116 contacting the underside of stop 117. Block 110 is moved downwardly during the routing and until guide 116 contacts the top of stop 117b. It is necessary to continue routing with raising block 110 or again lowering it, only if the first routing of the area between the upper and lower stop limits did not rout out the required depth for the recesses, and to do so until the desired depth is reached. The desired complementary recesses thus are prepared with movement of the router only vertically and into the work to the desired depth, and without any movement lengthwise parallel to the door and jamb (i.e., normal to standards 44).

Stud 198 is not an absolutely essential part of the special router bit, for in its essential requirements it is complete without the stud. The stud serves only as a convenient connecting link to facilitate ready attachment of the bit to a motor as by engagement of the stud by a chuck or collet at the operating end of the driving motor shaft. However, use of a stud is of considerable convenience because whenever the router bit teeth are sufliciently worn down to require changing, it readily can be removed from the stud and another such router bit head body substituted for it.

It can be seen that the router bit can be prepared by casting as with cast steel or by forging, in each case with respectively suitable molds or dies.

Alternatively, it can be machined from a disc-shaped work-piece, for example, cutting away with a milling cutter first the opposed segmental areas outside of the teeth, and then the open areas between them with an end mill to provide the vertical faces of the teeth, and by using a shaper if needed. The backwardly sloping planes abc and a'b'c then are prepared by mounting the work-piece with the stud held separately for each of them at the required angle in a vise mounted in a milling machine or grinder. Any surfaces requiring it then can be suitably ground.

Obviously, the router bit can be made with its teeth positioned as if they were a mirror image, for example,

of FIG. 2.

While the invention has been explained by detailed description of certain specific embodiments of it, it is understood that various modifications and substitutions can be made within the scope of the appended claims which are intended also to include equivalents of the specific embodiments.

What is claimed is:

1. A router bit having its cutting face perpendicular to tooth in the same way as the leading cutting edge of its axis of rotation, each outer tooth is located as to the rest of the outer (i) a plurality of circumferentially spaced apart, simitooth; the inner cutting edge of each inner tooth belarly shaped and outer positioned, substantially triangular cutting teeth with the leading cutting edge of each of them being parallel to said axis and based in the periphery of the circle of longest diameter outlined by the outermost point on said face, and the trailing outer peripheral face of each of which teeth recedes backwardly inwardly from said leading cuting perpendicular to its leading cutting edge and being spaced away at an acute angle from the outer end of a radius through its leading cutting point adequate to provide a suflicient angle of rake for its inner leading cutting edge; and the trailing plane through said last cutting edge and extending away from it receding progressively further away from ting edge away from a cylinder traced by the rotathe plane traced by rotation of said edge sufiiciently tion of said edge to provide adequately practical to provide adequate practical clearance; each respecclearance during routing; the inner cutting edge pertive tooth of each of said pluralities (i) and (ii) bependicular to said leading cutting edge at the leading so spaced from the next one of its plurality to ing cutting point forming a sufilcient angle of rake provide substantial balance during rotation whereby with the radius passing through said leading point said rotation is substantially free of vibration.

2. A router bit as claimed in claim 1, wherein each of outer face and inner cutting edge and the trailing said pluralities (i) and (ii) consists of a pair of teeth, edge joining them also receding toward said first each of which is diametrically opposite the other tooth mentioned outer face in a direction backwardly from of its respective pair. the leading cutting point to provide an adequately 3. A router bit as claimed in claim 1, wherein each of practical clearance; and said pluralities (i) and (ii) consists of three teeth, each (ii) a plurality of inner teeth triangularly shaped alike one of which is located radially about 120 degrees from and being similarly positioned relative to one aneach of the others of its three. other with each of them spaced apart from a respective one of said outer teeth to alternate with them; and with the body of each of the inner teeth being positioned within and spaced away from the periphof each of said teeth; and the face bounded by the References Cited UNITED STATES PATENTS ery of a circle traced by the leading cutting point of g '2 each of them, said circle being at least coincident 3700862 8/1965 ig g 144 27 with the circle traced by the inner end of the inner 5 5 3/1966 t n Z XR cutting edge of each of the outer teeth and at most o s em 3,319,672 5/1967 Phelps 144-27 XR only overlapping it by a distance radially significantly less than half of the largest thickness radially of an outer tooth; the leading cutting edge of each of the inner teeth being located as to the rest of such WILLIAM W. DYER, 111., Primary Examiner.

W. D. BRAY, Assistant Examiner.

Disclaimer and Dedication 3,381,728.-]|/2'lton Goldszfez'n. Long Beach, N.Y. ROUTING TOOL. Patent dated May 7, 1968. Disclai mer and dedication filed Apr. 24, 1968, by

the assignees, John Barsha, A. Abba Orlinger, and Milton Goldstein, as trustees.

Hereby disclaim and dedicate to the Public the terminal portion of the term of the patent subsequent to Mar. 8, 1983.

[Ofiicial Gazette August 15, 1.968.] 

1. A ROUTER BIT HAVING ITS CUTTING FACE PERPENDICULAR TO ITS AXIS OF ROTATION, (I) A PLURALITY OF CIRCUMFERENTIALLY SPACED APART, SIMILARLY SHAPED AND OUTER POSITIONED, SUBSTANTIALLY TRIANGULAR CUTTING TEETH WITH THE LEADING CUTTING EDGE OF EACH OF THEM BEING PARALLEL TO SAID AXIS AND BASED IN THE PERIPHERY OF THE CIRCLE OF LONGEST DIAMETER OUTLINED BY THE OUTERMOST POINT ON SAID FACE, AND THE TRAILING OUTER PERIPHERAL FACE OF EACH OF WHICH TEETH RECEDES BACKWARDLY INWARDLY FROM SAID LEADING CUTTING EDGE AWAY FROM A CYLINDER TRACED BY THE ROTATION OF SAID EDGE TO PROVIDE ADEQUATELY PRACTICAL CLEARANCE DURING ROUTING; THE INNER CUTTING EDGE PERPENDICULAR TO SAID LEADING CUTTING EDGE AT THE LEADING CUTTING POINT FORMING A SUFFICIENT ANGLE OF RAKE WITH THE RADIUS PASSING THROUGH SAID LEADING POINT OF EACH OF SAID TEETH; AND THE FACE BOUNDED BY THE OUTER FACE AND INNER CUTTING EDGE AND THE TRAILING EDGE JOINING THEM ALSO RECEDING TOWARD SAID FIRST MENTIONED OUTER FACE IN A DIRECTION BACKWARDLY FROM THE LEADING CUTTING POINT TO PROVIDE AN ADEQUATELY PRACTICAL CLEARANCE; AND (II) A PLURALITY OF INNER TEETH TRIANGULARLY SHAPED ALIKE AND BEING SIMILARLY POSITIONED RELATIVE TO ONE ANOTHER WITH EACH OF T*HEM SPACED APART FROM A RESPECTIVE ONE OF SAID OUTER TEETH TO ALTERNATE WITH THEM; AND WITH THE BODY OF EACH OF THE INNER TEETH BEING POSITIONED WITHIN AND SPACED AWAY FROM THE PERIPHERY OF A CIRCLE TRACED BY THE LEADING CUTTING POINT OF EACH OF THEM, SAID CIRCLE BEING AT LEAST COINCIDENT WITH THE CIRCLE TRACED BY THE INNER END OF THE INNER CUTTING EDGE OF EACH OF THE OUTER TEETH AND AT MOST ONLY OVERLAPPING IT BY A DISTANCE RADIALLY SIGNIFICANTLY LESS THAN HALF OF THE LARGEST THICKNESS RADIALLY OF AN OUTER TOOTH; THE LEADING CUTTING EDGE OF EACH OF THE INNER TEETH BEING LOCATED AS TO THE REST OF SUCH TOOTH IN THE SAME WAY AS THE LEADING CUTTING EDGE OF EACH OUTER TOOTH IS LOCATED AS TO THE REST OF THE OUTER TOOTH; THE INNER CUTTING EDGE OF EACH INNER TOOTH BEING PERPENDICULAR TO ITS LEADING CUTTING EDGE AND BEING SPACED AWAY AT AN ACUTE ANGLE FROM THE OUTER END OF A RADIUS THROUGH ITS LEADING CUTTING POINT ADEQUATE TO PROVIDE A SUFFICIENT ANGLE OF RAKE FOR ITS INNER LEADING CUTTING EDGE; AND THE TRAILING PLANE THROUGH SAID LAST CUTTING EDGE AND EXTENDING AWAY FROM IT RECEDING PROGRESSIVELY FURTHER AWAY FROM THE PLANE TRACED BY ROTATION OF SAID EDGE SUFFICIENTLY TO PROVIDE ADEQUATE PRACTICAL CLEARANCE; EACH RESPECTIVE TOOTH OF EACH OF SAID PLURALITIES (I) AND (II) BEING SO SPACED FROM THE NEXT ONE OF ITS PLURALITY TO PROVIDE SUBSTANTIAL BALANCE DURING ROTATION WHEREBY SAID ROTATION IS SUBSTANTIALLY FREE OF VIBRATION. 